Box-type solar ovens have been in existence since at least the 18th century. A comprehensive compendium of different box cookers from around the world was provided at http://solarcooking.wikia.com/wiki/Box_cookers (a printed copy of this website entitled “Box cookers—Solar Cooking,” dated 4 Feb. 2009, was included in the Information Disclosure Statement filed with the present application). The earliest designs were comprised of an insulated box with one or two glass panes forming a horizontal cover and window to the oven. When more than one glass pane is used for the window, an air gap is usually created between the two panes to form an insulation barrier. An example of this type of oven is illustrated in U.S. Pat. No. 3,391,688. Another variation involves inclining the upper of the two panes by some angle to position that pane relative to the position of the sun in the sky. An example of this type of oven, where the movable upper pane is attached to the lower box by a telescoping strip assembly, is illustrated in U.S. Pat. No. 4,220,141. In general, the size of the window to the box oven is sized as large as possible based on the adage that more sun light entering the box equals more heat within the box.
Many additional variations to box ovens have been developed over the years, including the addition of knobs or handles for the lid window, handles for the insulated base, and the development of dome shaped window lids (like the glass top of a cooking pot). The interior of such box ovens was typically the natural color of the material used to make it, such as tin, sheet metal and aluminum. The interior surface was often painted black to absorb heat, although the paint was often removed after multiple cleanings. If the interior is made of sheet glass, the glass can be painted black on the reverse side (which does not touch the food). The exterior surface of the box was usually its natural color and not painted, or no significance was attributed to the exterior color.
Since World War II, box ovens have been improved by the addition of a great variety of different exterior reflectors. U.S. Pat. Nos. 4,077,391, 4,125,109, 4,284,071, 4,292,957, 4,378,790 and 4,446,854, illustrate a base oven with one or more externally propagating reflector panes for directing sun light toward the base oven. U.S. Pat. No. 4,848,320 illustrates that the base may be turned at an angle toward the angle of the sun. U.S. Pat. Nos. 4,850,339 and 5,139,010 illustrate box ovens with lids than can be tilted to act as reflectors. U.S. Pat. No. 5,617,842 illustrates a base with a number of flower-petal shaped reflectors placed on a stand that can be oriented relative to the sun. Many of these box ovens are designed to generate enough heat at a cooking surface to boil water and fully cook foods, including meat, vegetable and grain meals, and are not portable, or easily portable. U.S. Pat. No. D259,694 does illustrate a more portable box oven with externally projecting reflectors.
In more recent years, solar ovens have largely moved away from the more traditional box design, such as toward parabolic cookers, such as that illustrated in U.S. Pat. No. 4,696,285, which includes a complicated frame assembly for adjusting for azimuth, declination and latitude to accurately track the position of the sun in the sky. A more untraditional design is illustrated by U.S. Pat. No. 5,893,360, which describes a large inflatable transparent bubble within which a food holding body can be placed when the bubble is inflated. United States Publication Number US2006/00501 illustrates one of the latest advancements in box oven design, where the box oven is electrically connected to an externally positioned solar panel.